By Ian Ransom
MELBOURNE (Reuters) - Reigning champion Lewis Hamilton topped the timesheets for Mercedes in a rain-hit first free practice at Formula One's season-opening Australian Grand Prix on Friday. The Briton bided his time until a break between rain squalls late in the 90-minute session at Albert Park and posted a lap of one minute 29.725 seconds, over four-tenths of a second quicker than Red Bull's Daniil Kvyat.
Kvyat's Australian team mate Daniel Ricciardo was third fastest, over a second adrift of Hamilton, and took a spill into the gravel late in the session as he pushed for a better time.
Four-times champion Sebastian Vettel, tipped to threaten Hamilton's ambitions of a third successive title, was first out of the garage in his Ferrari but failed to post a time as gusty winds buffeted the street circuit.
His team mate Kimi Raikkonen locked up and skidded at a turn, finishing with the 17th fastest time of the 20 cars that posted laps.
Force India's Nico Hulkenberg was fourth quickest ahead of Toro Rosso's teenager Max Verstappen.
Hamilton's team mate Nico Rosberg, who won the final three races of last season, was sixth quickest.
Toro Rosso's Carlos Sainz struggled with a reliability problem and was also unable to post a lap time.
New team Haas, the first U.S.-owned F1 outfit in 30 years, had a cautious debut with French driver Romain Grosjean the slowest and team mate Esteban Gutierrez 18th fastest.
(Editing by Nick Mulvenney)